Hello,
Anytime you add a new cat to a home, it can be stressful for everyone (human and feline). I would encourage you to visit our article on handling and socializing new cat in the house, since there are very likely some territorial concerns going on. As a general rule, I don’t recommend leaving food out and prefer meal feeding. By controlling when food is out and feeding each cat in a separate location, you can direct each one to their own space and at the same time, help eliminate competition for resources (food). It is also suggested to have 1 litter box per cat PLUS 1, so you should have 4 and they should be in different locations including different floors. This may help the new cat realize that he doesn’t always have to go to the basement. You have already done well to give the newer cat some time to adjust in his own room. It may take more time but it’s important to use positive reinforcement and still spend time with the previous residents so they feel they are not being replaced.
I hope this helps.
Dr. Ryan Llera
